Neonicotinoid insecticides (NNs) and the herbicide glyphosate are systemic pesticides widely used in agriculture and urban environments. They are the most used pesticides worldwide. Their extensive use has led to great social concerns regarding their environmental fate and toxicity to non-target organisms and to human health. Consequently, glyphosate is at risk of being banned in the EU and 3 NNs (imidacloprid, clothianidin and thiamethoxam) have recently been permanently banned for outdoor applications. Nevertheless, their use is still permitted in China. Moreover, NNs have been incorporated in the watch list of substances for the EU monitoring program in surface waters (2015/495/EU) due to possible threats to aquatic organisms. Therefore, these compounds are emerging environmental contaminants of concern.
This study investigates the temporal and spatial occurrence of 7 NNs, as well as other insecticides (fipronil, imidaclothiz, cycloxaprid and sulfoxaflor), the herbicide glyphosate and several of their transformation products in the Chinese Bohai Sea and its surrounding rivers. Water samples were collected in the summer and fall of 2018 from 36 rivers and 47 stations in the Bohai Sea. All samples were immediately stored at -20°C until analysis. All samples were extracted by solid-phase extraction (1L water sample was used for the insecticides, whereas 20 mL water sample was used for glyphosate and its main metabolite AMPA (aminomethylphosphonic acid)), eluted with methanol and further enriched by evaporation. For glyphosate and AMPA, the water samples were first derivatized with FMOC-Cl (9-Fluorenylmethoxycarbonyl chloride). All samples were analyzed by HPLC-MS/MS.
The results show that, from the 18 compounds analyzed, 15 were detected in river samples and 12 in seawater samples. Acetamiprid was detected in all river- and seawater samples. Much higher concentrations were observed in the rivers (